Atomically dispersed Cu coordinated Rh metallene arrays for simultaneously electrochemical aniline synthesis and biomass upgrading

Organic electrocatalytic conversion is an essential pathway for the green conversion of low-cost organic compounds to high-value chemicals, which urgently demands the development of efficient electrocatalysts. Here, we report a Cu single-atom dispersed Rh metallene arrays on Cu foam for cathodic nitrobenzene electroreduction reaction and anodic methanol oxidation reaction. In the coupled electrocatalytic system, the Cusingle-atom-Rh metallene arrays on Cu foam requires only the low voltages of 1.18 V to reach current densities of 100 mA cm−2 for generating aniline and formate, with up to ~100% of nitrobenzene conversion/ aniline selectivity and over ~90% of formate Faraday efficiency, achieving synthesis of high-value chemicals. Density functional theory calculations reveal the electron effect between Cu single-atom and Rh host and catalytic reaction mechanism. The synergistic catalytic effect and H*-spillover effect can improve catalytic reaction process and reduce energy barrier for reaction process, thus enhancing electrocatalytic reaction activity and target product selectivity.

By combining experiments and DFT calculations, the authors proposed the Cu dispersed Rh metallene arrays as new electrocatalysts for both Ph-NO2 ERR and MOR. However, there are several important computational evidence missing in their work, making it hard to be accepted. 1. How did they consider and construct the computational model in Fig. S18? Is it consistent with their experimental observation? 2. For Fig. S19, one cannot tell which one is Rh or Cu. 3. The coloring information is missing in Fig. S20, making it impossible to tell the charge transfer direction. 4. The quality of Fig. 6 should be further improved for clarity. H and I have repeated information, and they can be merged. 5. For the d-band center (they should mention that it is for the Rh atom to avoid misleading), a slight change from -1.77 to -1.79 eV cannot be considered as "a significant negative shift". It is not clear why a downshift of d-band center and occupancy of anti-bonding orbital "thus promoting a fast conversion of the reactants to key intermediates". 6. The most important one is, besides the adsorption energy calculations, the whole free energy profiles (including water dissociation) should be provided to support their proposed mechanisms of the two reactions. Detailed comparison should be done between those with and without the Cu. All the related data leading to these energy profiles should be summarized in supporting information.
Reviewer #3 (Remarks to the Author): In this paper, the authors synthesized Cu single-atom dispersed Rh metallene arrays on Cu foam and use them as electrocatalysts for the reduction of nitrobenzene and oxidation of methanol. Characterization of the catalyst was carried out using a combination of several techniques. The electrochemical reaction yielded the target products (aniline and formate) with high selectivity. A reaction mechanism is proposed using DFT calculations.
The reviewer carefully considered the paper. The publication in Nature Communications would require greater scholarly significance than in previous studies. However, the synthesis of aniline by electrooxidation of nitrobenzene and the synthesis of formic acid by oxidation of methanol have already been reported; thus, there is no novelty in the reactions. Although there may not be any studies combining these two reactions, as an electrolysis process, it is merely a combination of two known reactions.
The remaining novelty may lie in the performance of the catalyst. However, there are still doubts regarding the significance of the catalytic activity. While Table S2 compares the results with previous studies, it is important to note that the electrochemical reactions being compared are fundamentally different. Therefore, comparing voltages among different reactions does not hold significant meaning. Additionally, it should be noted that the majority of catalysts in previous studies were transition metal catalysts, while this study utilizes noble metals (which generally exhibit higher catalytic activity). Hence, making such comparisons may not be meaningful in this context.
For the above reasons, the reviewer has determined that this paper is not acceptable for publication in Nature Communications. Other comments are noted below.
The effect of Cu single-atom also seems unclear; the effect of Cu single-atom cannot be discussed without preparing Rh metallene arrays without Cu single-atom and comparing their catalytic activity. The comparison with Rh nanoparticles is made in the paper, but as mentioned in the paper, the surface areas are different between Rh NPs and Rh metallene. Therefore, the comparison may not be appropriate for discussing the effect of Cu single atoms due to the differences in surface area.
The authors stated the electronic interaction between Cu and Rh, but what is the density of Cu in the Rh metallene? If Cu is sparsely present on Rh metallene, there would be Rh atoms that do not interact with Cu. What is the percentage of Rh that the effect of Cu does reach?
There is a lack of discussion from an electrochemical point of view. At the very least, the standard redox potential should be given and overvoltages should be discussed.
Finally, the authors would need to check references. In the 52 references, only 4 papers are published by different nationalities than the authors. If appropriate works related to this study are cited, the reference list is no problem, but the reviewer is concerned about the large nationality bias in the reference list.
2 spillover effect and synergistic catalytic effect are promising strategies for applying in other organic electrocatalytic conversion reactions. Thus, this work is innovative. Please see Page 19.

Revision made in manuscript:
Please see Page 19. We have added the following revisions to the manuscript and highlighted them in the marked-up revised manuscript.
The superior Ph-NO2 ERR and MOR activity of CuSA-Rh MAs/CF originates from the following points: Firstly, the stable security wall-like structure formed by the ultrathin metallene arrays provides sufficient active sites and abundant interlayer channels. 45 Secondly, the inherent defect-rich structure and low-crystalline regions of CuSA-Rh MAs/CF can induce unsaturated coordination metallic bonds and optimize the local electron structure. 37,46 Thirdly, the synergistic catalysis effect and H*-spillover effect between Cu single-atom and Rh host can optimize the catalytic reaction process, facilitate the stable and rapid conversion of reactants to intermediates as well as accelerate the desorption of target products. Fourthly, the Cu single-atom as effective adsorption sites can modulate the competition for adsorbate adsorption on Rh sites thus promoting electrocatalytic reactions.

Comment 1-2:
The authors need to further confirm the existence of copper-copper atoms by EELS with high-resolution transmission electron microscopy.
Reply 1-2: Thanks for the value suggestion. We have confirmed the existence of Rh and Cu elements by EELS analysis. As revealed by the EELS of CuSA-Rh MAs, the energy loss peak around 498.8 eV can be assigned to the Rh M electron transition (Please see Ref. 46. Adv. Mater. 2020, 32, 1908521 andRef. 47. Adv. Mater. 2021, 33, 2007894), and the energy loss peak around 933.1 eV can be assigned to the Cu L electron transition (Please see Ref. 48. Appl. Surf. Sci. 2021, 563, 150318    The Rh/Cu atomic ratio was further determined to be approximately 93.6/6.4 via the TEM energy dispersive X-ray spectroscopy (TEM-EDS, Fig. S4). The mass ratio (Rh/Cu = 95.1/4.9) and atomic ratio (Rh/Cu = 92.6/7.4) of Rh/Cu in CuSA-Rh MAs were further analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) (Fig. S5), which is close to the results obtained from TEM-EDS.
In the X-ray diffraction (XRD) pattern (Fig. 1h)    Reply 1-5: Thanks for the value suggestion. We have carefully checked the whole manuscript and corrected the grammatical and spelling errors in the manuscript.
Comment 1-6: The authors need to provide the XRD\XPS\HRTEM data of the CuSA-Rh MAs/CF sample after the catalytic performance test to prove the stability of the catalyst.
Reply 1-6: Thanks for the value suggestion. We have provided the XRD\XPS\HRTEM data of the CuSA-Rh MAs/CF to prove the stability of the catalyst. Based on the results of SEM, TEM and HRTEM images, after stability testing, no significant degradation is observed for the morphology and structure of CuSA-Rh MAs/CF, and the crystal structure of CuSA-Rh MAs remains stable.
Moreover, XPS results before and after stability testing illustrate that the elements composition and chemical state for CuSA-Rh MAs remain stable after stability testing. Please see Page 15 and Figs.

S21-S22.
Revision made in manuscript: Please see Page 15. We have added the following revisions to the manuscript and highlighted them in the marked-up revised manuscript. Furthermore, after stability testing, no significant degradation is observed for the morphology and structure of CuSA-Rh MAs/CF (Figs. S21a-S21b), and the crystal structure of CuSA-Rh MAs remains stable (Figs. S21c-S21d). Notably, Fig. S22 further reveals that the elemental composition and chemical state of CuSA-Rh MAs show no significant change after stability testing. These conclusions indicate a superior stability for the Ph-NO2 ERR-MOR coupling system constructed by the CuSA-Rh MAs/CF.

Revision made in supporting information:
Please see Pages S14-S15 and Figs. S21-S22. We have added the following revisions to the supporting information.    In the X-ray diffraction (XRD) pattern (Fig. 1h), the characteristic peaks of CuSA-Rh MAs can be assigned to a typical face-centered cube (fcc) metallic Rh phase (No. 05-0685).
The Cu single-atom was analyzed by AC-HAADF-STEM image and 3D topographic atom images. 2b, c). The corresponding integrated pixel intensity profile also illustrates the isolated low-intensity Cu atoms dispersed surrounding the high-intensity Rh atoms on the crystal surface ( Fig. 2d), further proving the presence of isolated Cu single-atom on the CuSA-Rh MAs.
Notably, based on the WT spectra analysis for CuSA-Rh MAs and Rh foil (Fig. 2i), the Rh-Rh/Cu-Rh intensity maximum of CuSA-Rh MAs exhibits a negative shift of about 0.33 Å -1 compared with Rh-Rh intensity maximum of Rh foil, which is induced by the coordination of the Cu-Rh bond.
The Cu K-edge EXAFS spectra show the distinct peak of CuSA-Rh MAs at 2.43 Å ascribed to the Cu-Rh bond, obviously distinct with Cu-Cu (2.23 Å) and Cu-O (1.51 Å) bands (Fig. 2k), revealing the presence of dispersed Cu single-atom.
As displayed in   Revision made in supporting information: Please see Page S5. We have added the following revisions to the supporting information.
Based on experimental results, the CuSA-Rh MAs display the single-phase fcc crystal structure and single-atom alloy structure. In the DFT simulation process, the Rh model is firstly constructed, and the Cu single-atom is induced with a random distribution, we used the fcc cubic phase of the original Rh as a template to build a 3×3×3 supercell containing 108 atoms for CuSA-Rh MAs, the atom ratio of Rh : Cu is approximately 93 : 7.      The blue, red, and white spheres represent Rh, Cu, and H atoms respectively. (j) Optimized structures of MOR intermediates on CuSA-Rh (111). The blue, red, gray, cyan, and white spheres represent Rh, Cu, C, O, and H atoms respectively. (k) Comparison of free energy profiles for MOR pathway on CuSA-Rh (111) and Rh (111).
Revision made in supporting information: Please see Page S19 and Fig. S33. We have added the following revisions to the supporting information.  Catal. 2022, 12, 14062-14071). Moreover, based on further analysis of charge density difference for adsorbed Ph-NO2* on CuSA-Rh (111) and Rh (111), the electron transfer between CuSA-Rh and Ph-NO2* (0.19 e) is smaller than that between Rh and Ph-NO2* (0.25 e) owing to the electron interaction between Cu single-atom and the Rh host, which eventually can induce the decrease of electron interaction between CuSA-Rh and Ph-NO2*, thus weakening the binding of Ph-NO2* on CuSA-Rh (Please see Ref. 43. Adv. Funct. Mater. 2023, 33, 2209890), which is consistent with the results of adsorption energy. Secondly, there is electron accumulation in the antibonding orbitals for both CuSA-Rh and Rh, which favors the weakening of the bond energy for the N-O bond thus facilitating the conversion of Ph-NO2* to key intermediates (Please see Ref. 43. Adv. Funct. Mater. 2023, 33, 2209890 andRef. 56. Adv. Energy Mater. 2020, 10, 1903038). Moreover, as displayed in Fig. 6d, the d-band center of Rh-4d orbitals for CuSA-Rh (111) (-1.79 eV) exhibits a slight negative shift compared with Rh (111) (-1.77 eV). It is notable that the PDOS for Rh-4d of CuSA-Rh bulk (-1.82 eV) and Rh bulk (-1.49 eV) also reflect the similar trend (Fig. S26). Fig. S27 and Table S4, The electron transfer between CuSA-Rh and Ph-NO2* (0.19 e) is smaller than that between Rh and Ph-NO2* (0.25 e) owing to the electron interaction between Cu single-atom and the Rh host, which eventually can induce the decrease of electron interaction between CuSA-Rh and Ph-NO2*, thus weakening the binding of Ph-NO2* on CuSA-Rh. 43 Notably, there is electron accumulation in the antibonding orbitals for both CuSA-Rh and Rh, which favors the weakening of the bond energy for the N-O bond. 43, 56 These conclusions indicate that the electron interaction between the isolated Cu single-atom and the Rh host causes a downshift of the d-band center and a decrease in the electron interaction between the catalyst and adsorbate, thus promoting a fast conversion of the reactants to key intermediates as well as optimizing the desorption of the target product. 8,43 Moreover, Fig. S28a and Table S5 present the optimized adsorption structure and adsorption energy (∆Eads) of Ph-NO2 on Rh (111) and CuSA-Rh (111) surfaces. The calculated Ph-NO2 ∆Eads of CuSA-Rh (111) is -1.08 eV, which is lower than that of  Revision made in supporting information: Please see Pages S16, S17, S23, S24 and Figs. S26, S27, S28a and Table S4-S5. We have added the following revisions to the supporting information.   Comment 2-6: The most important one is, besides the adsorption energy calculations, the whole free energy profiles (including water dissociation) should be provided to support their proposed mechanisms of the two reactions. Detailed comparison should be done between those with and without the Cu. All the related data leading to these energy profiles should be summarized in supporting information.

As shown in
Reply 2-6: Thanks for the value suggestion. We have provided the whole free energy profiles of the two reactions and the energy profiles of the H2O dissociation process to illustrate the enhanced mechanism of the electrocatalytic reaction. All the related data leading to these energy profiles have been summarized in supporting information. For Ph-NO2 ERR, the free energy profiles of optimized intermediates for Ph-NO2 ERR pathway reveal Ph-NOH*→Ph-NHOH* and Ph-NH2*→Ph-NH2 as the rate-determining step (RDS) for CuSA-Rh and Rh, respectively. Obviously,  Table S3-S10.

Revision made in manuscript:
Please see Pages 17, 18 and Fig. 6e, 6f, 6g, 6j, 6k. We have added the following revisions to the manuscript and highlighted them in the marked-up revised manuscript.
Moreover, the free energy profiles of optimized intermediates for Ph-NO2 ERR pathway reveal Ph-NOH*→Ph-NHOH* and Ph-NH2*→Ph-NH2 as the rate-determining step (RDS) for CuSA-Rh and Rh, respectively (Figs 6e-6f and Fig. S29). Obviously, the CuSA-Rh exhibits a lower energy barrier (0.74 eV) on the RDS compared with Rh (0.85 eV) ( Fig. 6f and Table S6), further indicating the higher ability on CuSA-Rh for driving the Ph-NO2 ERR to Ph-NH2. Fig. 6g and Fig. S30 display the calculated energy profiles of H2O dissociation process and corresponding optimized structures of the initial, transition and final states. The energy barrier for H2O dissociation of CuSA-Rh (0.83 eV) is lower than that of Rh (1.01 eV) ( Fig. 6g and Table S7), indicating that the introduction of the Cu single-atom is beneficial for the dissociation of H2O on CuSA-Rh to facilitate the formation H* for Ph-NO2 hydrogenation.
For further investigating the MOR mechanism on CuSA-Rh MAs, the free energy profiles of optimized intermediates for MOR pathway were analyzed by the DFT calculations (Fig. 6j-6k and   Fig. S32). It can be observed that the CuSA-Rh possesses a lower energy barrier for RDS (CH2O*→CHO*, 0.55 eV) compared to the RDS (CHO*→HCOOH*, 0.62 eV) of Rh ( Fig. 6k and Table S9), indicating a more favorable MOR process on CuSA-Rh.
Meanwhile, Fig. 6k further shows that the energy barrier for the desorption step (HCOOH*→HCOOH) of CuSA-Rh (0.43 eV) is lower than that of Rh (0.54 eV).

Revision made in supporting information:
Please see Pages S17, S18 and Pages S22-S29 and Figs. S29, S30, S32 and Table S3-S10. We have added the following revisions to the supporting information.

Reviewer #3
Comment: In this paper, the authors synthesized Cu single-atom dispersed Rh metallene arrays on Cu foam and use them as electrocatalysts for the reduction of nitrobenzene and oxidation of methanol. Characterization of the catalyst was carried out using a combination of several techniques.
The electrochemical reaction yielded the target products (aniline and formate) with high selectivity.
A reaction mechanism is proposed using DFT calculations. The reviewer carefully considered the paper. The publication in Nature Communications would require greater scholarly significance than in previous studies. However, the synthesis of aniline by electro-oxidation of nitrobenzene and the synthesis of formic acid by oxidation of methanol have already been reported; thus, there is no novelty in the reactions. Although there may not be any studies combining these two reactions, as an electrolysis process, it is merely a combination of two known reactions. The remaining novelty may lie in the performance of the catalyst. However, there are still doubts regarding the significance of the catalytic activity. While Table S2 compares the results with previous studies, it is important to note that the electrochemical reactions being compared are fundamentally different. Therefore, comparing voltages among different reactions does not hold significant meaning. Additionally, it should be noted that the majority of catalysts in previous studies were transition metal catalysts, while this study utilizes noble metals (which generally exhibit higher catalytic activity). Hence, making such comparisons may not be meaningful in this context. For the above reasons, the reviewer has determined that this paper is not acceptable for publication in Nature Communications.
Other comments are noted below.

Reply:
We thank Referee #3 for his/her valuable time reviewing our manuscript. We also appreciate his/her comments. Although Ph-NO2 ERR and MOR have been reported so far, in this work, we constructed for the first time Cu single-atom coordinated Rh metallene array structure and proposed the unique mechanisms (H*-spillover effect and synergistic catalytic effect) to enhance the activity and selectivity of Ph-NO2 ERR and MOR, which is different from the previously reported work.
More importantly, we constructed the CuSA-Rh MAs/CF as a bifunctional catalyst applied in a novel Ph-NO2 ERR-MOR two-electrode system, which achieves the simultaneous generation of highvalue chemicals at the cathode and anode. Meanwhile, we proved the unique mechanism of the introduction of Cu single-atom on the enhancement of catalytic activity by a series of experiments and DFT calculations. The design of this single-atom alloy metallene structure and the use of H*-spillover effect and synergistic catalytic effect are promising strategies for applying in other organic electrocatalytic conversion reactions. Thus, this work is innovative. Moreover, your comments on the catalytic performance comparison table are extremely important, we have removed the previous   Table S2 and developed a new table. Based on the new Table S2, apart from comparing noble metal catalysts, we also further compared non-noble metal catalysts. Although the designed catalyst (CuSA-Rh MAs/CF) in this work is a noble metal-based catalyst, due to the synergistic catalytic effect and H*-spillover effect caused by the interaction of Cu single-atom and Rh host, the CuSA-Rh MAs/CF exhibits a lower electrolysis potential (-0.1 V vs. RHE) and electrolysis time (1 h) to achieve a higher Ph-NO2 conversion (~100%) and Ph-NH2 selectivity (99.7%), which is significantly higher than previously reported noble metal based/non-noble metal-based catalysts.
Please see Page 11 and Table S2.

Revision made in manuscript:
Please see Page 11. We have added the following revisions to the manuscript and highlighted them in the marked-up revised manuscript.
Notably, the activity and selectivity of Ph-NO2 ERR to Ph-NH2 on CuSA-Rh MAs/CF are also superior to several reported electrocatalysts (Table S2). Table S2. Comment 3-1: The effect of Cu single-atom also seems unclear; the effect of Cu single-atom cannot be discussed without preparing Rh metallene arrays without Cu single-atom and comparing their catalytic activity. The comparison with Rh nanoparticles is made in the paper, but as mentioned in the paper, the surface areas are different between Rh NPs and Rh metallene. Therefore, the comparison may not be appropriate for discussing the effect of Cu single atoms due to the differences in surface area. ECSAs for various electrocatalysts were evaluated by the electrochemical Cdl calculated based on CV curves, the Cdl value for CuSA-Rh MAs/CF (49.9 mF cm -2 ) was calculated to be higher than those of Rhene-CF (35.9 mF cm -2 ), Rh NPs-CF (17.1 mF cm -2 ) and CF (2.1 mF cm -2 ), which reveals the rich active sites in CuSA-Rh MAs/CF due to the ultrathin metallene array structure and the introduction of isolated Cu single-atom. These conclusions demonstrate that the ultrathin metallene structure and the introduction of isolated Cu single-atom are beneficial for improving Ph-NO2 ERR and MOR activity. Please see Page 11, 13, 14 and Figs. S14, S15, S17, S18, S19, S20.

Revision made in manuscript:
Please see Pages 11, 13, 14. We have added the following revisions to the manuscript and highlighted them in the marked-up revised manuscript.
The improved activity of Ph-NO2 ERR to Ph-NH2 for CuSA-Rh MAs/CF originates from the ultrathin metallene array structure and the synergistic effect of isolated Cu single-atom with Rh host.
It is worth mentioning that the CuSA-Rh MAs/CF possesses a superior MOR activity compared with Rhene-CF, Rh NPs-CF and CF (Fig. S17a). Meanwhile, relative to the standard potential (0.103 V vs. RHE) of MOR, 17 the overpotential of CuSA-Rh MAs/CF is 1.25 V (vs. RHE) for reaching a current density of 20 mA cm -2 , which is lower than those of Rhene-CF (1.30 V vs. RHE), Rh NPs-CF (1.31 V vs. RHE) and CF (1.35 V vs. RHE) (Fig. S17b).
Furthermore, the H* ∆Eads of various sites (A to E) were further calculated for investigating the hydrogenation mechanism of H* with H2O as the hydrogen source on CuSA-Rh MAs (Figs. 6h-6i).
Visually, the variation of H* ∆Eads from A to E sites on CuSA-Rh reveals a gradually increased H* adsorption ( Fig.6i and  The blue, red, and white spheres represent Rh, Cu, and H atoms respectively.

Revision made in supporting information:
Please see Page S16 and Figs. S24-S26 and Table S3 and Table S8. We have added the following revisions to the supporting information.

Comment 3-3:
There is a lack of discussion from an electrochemical point of view. At the very least, the standard redox potential should be given and overvoltages should be discussed.

Reply 3-3:
Thanks for the value suggestion. We have discussed the standard redox potential and

REVIEWERS' COMMENTS
Reviewer #1 (Remarks to the Author): All the comments and suggestions from the reviewers have been replied very well. The quality of the revised manuscript is satisfied. I recommend its acceptance in Nature Communications.
Reviewer #2 (Remarks to the Author): The authors have tried to address my previous concerns about the insufficient computational evidence. The current version with more details is clearly much better and can provide a stronger support for their proposed possible reaction mechanism resulting in the good catalytic performance of synthesized catalysts.
Reviewer #3 (Remarks to the Author): I have evaluated the authors' responses. However, the major concern I raised, which is whether this paper has the novelty to be published in Nature Communications, is still not clear.
Firstly, as the authors themselves acknowledge, the reactions covered in this paper are well-known and are simply combined here. While the authors claim there are some novelties related to DFT calculations, I cannot evaluate them due to not being within my expertise, so I will leave that aside. However, since the main focus of this study is electrochemical reactions, innovative performance in these reactions must be needed for publication in Nature Communications. With this in mind, I examined the revised Table S2. In Table S2, a comparison between the hydrogenation of nitrobenzene in this paper and previous studies is provided.
I have reviewed all the papers shown in Table S2. As I mentioned in my previous comments, it is not appropriate to compare precious metal catalysts and transition metal catalysts on the same level. Furthermore, it is essential to emphasize that the reaction conditions differ between previous papers and this work, making a direct comparison of potential, conversion, and selectivity meaningless. For example, in ref 5, the reaction is performed with 0.1 M nitrobenzene, which is significantly higher than your paper (5 mM). Additionally, the electrolyte used is not consistent. While you used KOH, previous studies often employed sodium sulfate and others. Furthermore, the amount of catalysts on an electrode would be different. In other words, comparing potential, conversion, and selectivity in reactions with entirely different pH, substrate concentrations, and ESCA of catalysts does not prove the superiority of your research.
Moreover, most of the papers listed in Table S2 are not from high-impact journals. If you wish to emphasize excellent catalytic performance in Nature Communications, it is also crucial to consider what the comparison papers are.
Based on the points mentioned above, due to the lack of clarity on the significance of this paper's electrochemical reactions, I cannot approve its publication in Nature Communications.

Reviewer #3
Comment: I have evaluated the authors' responses. However, the major concern I raised, which is whether this paper has the novelty to be published in Nature Communications, is still not clear.
Firstly, as the authors themselves acknowledge, the reactions covered in this paper are well-known and are simply combined here. While the authors claim there are some novelties related to DFT calculations, I cannot evaluate them due to not being within my expertise, so I will leave that aside.
However, since the main focus of this study is electrochemical reactions, innovative performance in these reactions must be needed for publication in Nature Communications. With this in mind, I examined the revised Table S2. In Table S2, a comparison between the hydrogenation of nitrobenzene in this paper and previous studies is provided. I have reviewed all the papers shown in Table S2. As I mentioned in my previous comments, it is not appropriate to compare precious metal catalysts and transition metal catalysts on the same level. Furthermore, it is essential to emphasize that the reaction conditions differ between previous papers and this work, making a direct comparison of potential, conversion, and selectivity meaningless. For example, in ref 5, the reaction is performed with 0.1 M nitrobenzene, which is significantly higher than your paper (5 mM).
Additionally, the electrolyte used is not consistent. While you used KOH, previous studies often employed sodium sulfate and others. Furthermore, the amount of catalysts on an electrode would be different. In other words, comparing potential, conversion, and selectivity in reactions with entirely different pH, substrate concentrations, and ESCA of catalysts does not prove the superiority of your research. Moreover, most of the papers listed in Table S2 are not from high-impact journals. If you wish to emphasize excellent catalytic performance in Nature Communications, it is also crucial to consider what the comparison papers are. Based on the points mentioned above, due to the lack of clarity on the significance of this paper's electrochemical reactions, I cannot approve its publication in Nature Communications.

Reply:
We thank Referee #3 for his/her valuable time reviewing our manuscript. We also appreciate his/her comments. Your comments on the catalytic performance comparison table are extremely important, we have removed the Table S2 in the revised manuscript based on your suggestions.
Moreover, as previously mentioned, although Ph-NO2 ERR and MOR have been reported so far, there are some important distinctions that make our work different from previously reported work and contribute to its novelty. Firstly, we constructed for the first time Cu single-atom coordinated